Why do I have this recurring dream?

I find myself in the roof top of a skyscraper and no way to go down except to jump.No doors,no windows ,nothing.Not even a phone.
I am sitting there alone thinking if jumping from such a high building could really save my life..
I am extremely nervous, shivering and sweating profusely ..
Cried aloud a few times but nobody hears..and All I want is to get down safely,that's on my mind ,until I wake up and find myself totally drenched in perspiration.

This is probably the 3rd time I am experiencing this strange dream..

Any ideas why ?